Sam's confidence that China cannot project serious power as far as Australia is not justified by China's lack of capability per se, but by his confidence that another big power, presumably the US, would stop it. If China was not opposed by another major power, it could already project very substantial forces our way.

Actually, my confidence is justified by China's capability. I follow Chinese military developments pretty closely, but I don't know which 'very substantial forces' Hugh is referring to. Yes, China does have global power projection capabilities of some kinds: nuclear weapons, for example, and probably cyber-attack capabilities.

But Hugh's remarks are made in the context of Australia's combat aircraft fleet. What type of forces does China have that would justify more than 100 frontline RAAF aircraft?

I ask this question not on the premise that the US is sticking around. Even if Washington pulled up stumps from the Asia Pacific tomorrow, I don't think China could send military forces in our direction that would justify more than three frontline squadrons of fighters.

China couldn't send bombers (the fleet is old and slow with insufficient range; see image, courtesy of Sinodefence) or fighters (China doesn't have the aerial tanker support to send them beyond the first island chain) or amphibious forces (they're growing and modernising, but mainly with the aim of crossing the Taiwan Strait) and certainly not aircraft carriers (even if China's sole carrier was operational, its air complement would be tiny and not terribly effective; should China decide to build more carriers, we will get plenty of warning time).

You could point to China's submarine fleet as an exception here; it has not only modernised quite rapidly (though it's still well behind the US and Russia) but patrols are becoming more frequent. Still, you don't need a fighter fleet to find submarines; you need anti-submarine aircraft and your own submarines. For those reasons and others, I support a larger sub fleet. But fighters? I just can't see it.

As for Australia needing 'middle-power strategic weight' for reasons other than China, don't we already have that now? When you make rough comparisons with other countries in our population and GDP range (the Netherlands, Canada) you find that our military forces are of similar weight. Of course, we face a more uncertain strategic environment than those countries do. But even when you make the more important comparison, that with our regional neighbours, you find that Australia is comfortably ahead of all Southeast Asia, with the partial exception of Singapore. Why isn't that enough?